This offer is through groupon which offer £6 for each recommendation which buys an offer (even one which costs much less)

You can sign up an account then reccomend yourself by sending a link to a different email then signing up again and buying the painballing. Your first account is then credited with £6 credit. You could do this many times and build up a decent amount and use that to buy their already heavily discounted products.

And i have been painballing here before and it was the best paintballing site i had been to. Very professional and competitivly priced on balls.